Electron discharge device



Jan. 1, 1952 H. 3. ANDERSON 2,580,988

ELECTRON DISCHARGE DEVICE Filed April 15, 1948 Patented Jan. 1, 1952 ELECTRON DISCHARGE DEVICE Homer G. Anderson, Newtonville, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application April 15, 1948, Serial No. 21,122

12 Claims.

This invention relates to electron discharge devices, and more particularly to a cathode structure for devices of the so-called magnetron type. I

An object of this invention is to devise a novel direcly-heated cathode structure which is intended to operate at high temperatures.

Another object is to provide a cathode structure which operates to very eifectively prevent emission of electrons from the cathode in undesired directions.

A further object is to devise a cathode structure by means of which the end shields may be maintained substantially cooler than is possible with prior structures.

A still further object is to devise a cathode structure which will provide increased conduction of heat away from the end shields of a magnetron cathode.

An additional object is to devise a novel cathode structure for magnetrons.

The foregoing and other objects of the invention will be best understood from the following description of an exemplification thereof, reference being had to the accompanying drawing, wherein:

Fig. 1 is a vertical section through an electron discharge device utilizing a cathode assembly according to this invention;

Fig. 2 is a section taken on line 2-2 of Fig. 1;

Fig. 3 is a partial view of the cathode assembly of Fig. 1 on an enlarged scale;

Fig. 4 is an enlarged section taken on line 4-4 of Fig. 3; and

Fig. 5 is a view taken looking at the upper end of Fig. 3, part of the structure being broken away to show details thereof.

The illustrative embodiment of the present invention shown comprises a cylindrical envelope I of an electron discharge device of the so-called magnetron type, hermetically sealed at both ends by caps 2 and 3. Said envelope and caps may and preferably will be made of copper. Upon the inner surface of said envelope there is provided a central, circular projection A to which are soldered a plurality of suitably-spaced, radially-disposed plates 5, the inner ends of which constitute anode faces. Said plates 5 will preferably be stamped from a sheet of highly conductive copper.

Alternatively, instead of the above construction, the structure between the upper and lower faces of the plates 5, including the central portion of the envelope, may be formed by a vertically-superposed stack of horizontally-disposed laminations, each lamination including a plurality of radial arms and an outer continuous annular ring. In such a construction, upper and lower annular rings cut from a solid block of copper would be placed respectively adjacent the upper and lower ends of the stack of laminations to complete the cylindricalenvelope.

In order to eliminate'spurious oscillations in the completed magnetron, each anode member 5 is provided, in its upper and lower edges, with slots 6 and 1, respectively, in each of which slots is positioned a pair of concentrically-disposed, spaced circular conducting straps, the pair in the upper slot 6 being indicated by 8 and 9 and the pair in the lower slot 1 being indicated by l0 and H. The straps 8 and 9 alternately contact successive anode members 5, and are supported thereby, by means of vertically-extending fingers which extend from the bottom of the straps and are fastened to the respective anode members at the base of slots 6.. Similarly, the straps l0 and H alternately contact successive anode members 5, and are supported thereby, by means of vertically-extending fingers which extend from the top of the straps and are fastened to the respective anode members at the upper faces of slots 1. In this way, alternate anode members are always maintained at the same instantaneous potential.

Adjacent the end caps 2 and 3 are the usual pole pieces 12 and I3 associated with the magnetron type of electron discharge device, these pole pieces serving to generate a substantially uniform magnetic field in a direction parallel to the longitudinal axis of the cylindrical envelope I.

The anode faces constituted by the inner ends of plates or vanes 5 cooperate with a cathode [4 supported substantially centrally of said anode faces, said cathode being of the directly-heated type and including as the heart thereof an electron-emissive portion in the form of a cylindrical sleeve l5. Sleeve I5 preferably consists of compressed, intimately admixed powdered thoria and a powdered refractory metal, metal compound or metal alloy, as disclosed and claimed in the copending application of John F. Hanson, Ser. No. 753,864, filed June 11, 1947, now Patent No. 2,477,601, dated August 2 1949, and is fabricated or molded as disclosed in the aforesaid Hanson application.

A cylindrical sheet metal supporting sleeve I6, of molybdenum for example, is rigidly secured, as by platinum brazing, to the upper horizontal end face of sleeve 15, while a similar supporting -3 sleeve 11 is similarly secured to the lower horizontal end face of said sleeve. Sleeves l3 and I1 may be positioned substantially centrally radially of the end facesfoi sleeve 15. Sleeves l6 and I1 may be stamped out of thin sheet metal and thereafter bent into cylindrical shape. In order to decrease the heat losses by conduction through the metal sleeves l8 and H from the emissive sleeve l5, it being desirable not to abstract heat from the emissive sleeve but to maintain said sleeve I! at a high temperature for ample electron emission, a heat choke is provided in each of the sleeves i8 and i1. Each heat chokirincludes a plurality, for example five, of equally-spaced horizontal substantially rectangular slots l8 and a plurality, for example five, of equally-spaced vertical substantially rectangular slots it, the vertical and horizontal slots alternating around the circumference of each sleeve is and i1 and/the slots extending entirely through the sleeves, as shown in Fig. 4. By thus reducing the metallic cross-section of each of sleeves l8 and H by these gaps or spaces,

the conduction of-heat by such sleeves is greatly reduced.

Light, protective annular horizontal sheet metal shields 20 and 2|, respectively, of molybdenum or other suitable material, are provided between the upper end of upper-"sleeve l3 and the envelope cap 2, and between the lower end of lower sleeve l1 and the envelope cap 3. Upper shield member 28 is secured, as by platinum brazing, to the upper end of upper sleeve l6 concentrically with the common longitudinal axis of sleeves Ii1, while lower shield member 2| is similarly secured to the lower endof lower sleeve i1 concentrically with the longitudinal axis of sleeves l5l|. The inner diameter of annular members and 2| is substantially equal to the inner diameter of emisslve sleeve ii, while the outer diameter of said annular members is greater than the outer diameter of sleeve i5. These shields 28 and 2! prevent electrons emitted from the exterior of sleeve from traveling in oblique upward and downward directions toward the two envelope caps 2 and 3.

A lead-in cathode support and conductor 22 is sealed into an inner glass tube 23 at-24. l The inner tube 23 is sealed, at its outer end, at a point oi! the drawing, to the outer end of a concentric outer glass tube 25, the inner end of which is sealed to a conducting pipe 2i which is hermetically secured to a bushing 21 provided on envelope I adjacent the upper end thereof. A second leadin cathode support and conductor 28 is sealed into an inner glass tube 29 at 38. The inner tube 28 is similarly sealed, at its outer end, to the outer end of a concentric outer glass tube 3|, the inner end of which is similarly sealed to a conducting pipe 32 which is hermetically secured to -a bushing 33 provided on envelope i adjacent the lower end thereof. The longitudinal axes of conductors 22 and 28 are substantially in vertical alignment, and such axes, as well as the planes of shield members 28 and 2 i are transverse to the longitudinal axis of sleeves lS-li.

An upper metallic supporting member 32, made of molybdenum or other suitable metal, has a planar somewhat hour-glass-shaped inner end and an outer semicircular or somewhat tubular outer end. As may be seen in Fig. 5, the inner end of member 34 is rigidly secured, as by brazing, at a plurality of spaced points on its lower surface, such as at the four corners at the enlarged ends of the hour-glam portion, to the a,sso,oss

upper surface of upper shield 20, the hour-glass portion spanning the central opening in said shield. The outer end of member 34 has a curvature which matches the curvature of the inner end of lead-in conductor 22, and this end is firmly secured, as by brazing, to the inner end of conductor 22, to thereby firmly attach and electrically connect shield member 28 to conductor 22. A lower metallic supporting member 35, also made of molybdenum or other suitable metal, has the same configuration as does member 34. The upper surface of the inner end of member 35 is similarly rigidly secured to the lower surface of lower shield2l, while the outer end of said member is secured to the inner end of conductor 28, to thereby firmly attach and electrically connect shield member 2i to condoctor 23. Since shield members 20 and 2| are firmly secured to opposite ends of sleeve 15 through sleeves i6 and i1, respectively, it should be seen that the cathode sleeve i5 is firmly supported between and by conductors 22 and 28.

Light, protective imperforate horizontal disk sheet metal shields 38 and 31, respectively, of molybdenum or other suitable metal, are provided between the upper side of upper supporting member 34 and the envelope cap 2, and between the lower side of lower supporting members 35 and the envelope cap 3. The planes of shield members 36 and 31 are substantially parallel to those of members 20 and 2| and transverse to the longitudinal axis of sleeves l5i|, and shield members 36 and 31 are spaced from the respective adjacent and corresponding members 20 and 2!. The diameter of members 38 and 31 is substantially equal to the outer diameter of members 20 and 2|.

In order to maintain shield 35 above and properly spaced from shield 28 and supporting member 34, a substantially U-shaped bracket 38 is positioned sidewise between the upper surface of supporting member 34 and the lower surface of shield 36, at a position at the extreme inner end of member 38 or diametrically opposite leadin 22 which terminates outside the outer limit of disk member 33. The bracket 38 is formed from sheet metal, and the face areas of the legs of the U are extremely small as compared to the area of annular member 28 or to the area of the longer leg being similarly secured to the lower face of disk 38. A similar metallic U-shaped bracket 33 is positioned sidewise between the lower surface of member 35 and the upper surface of shield 31, diametrically opposite lead-in 28, the shorter leg of this bracket being secured to the lower side of member 35 and the longer leg thereof being secured to the upper face of disk 31. By means of the brackets 38 and 38, the sides "of disks 36 and 31 opposite to the respective leadins 22 and 28 are held spaced from the corresponding members 20, 34 and 2!, 35 and are at the same time electrically connected to the said corresponding members.

36, at the lead-in side thereof, while the outer end of said member is fastened to and around the tubular outer end of supporting member 34. A similar lower supporting member 4I is provided, the planar inner end of which is fastened to the lower face of disk 31 at the lead-in side thereof and the outer end of which is fastened to and around the tubular outer end of supporting member 35. In this way, the lead-in sides of disks 36 and 3'! are maintained in positions spaced from the respective shield members 20 and 2 I, the disks lying substantially parallel to the annular shield members and being electrically connected to the respective lead-ins 22 and 28.

The lead-ins 22 and 28 provide a pair of conductors for cathode heating and for cathode supporting purposes. It may be seen that the entire cathode assembly, including elements I5, I6, I1, 26, 2 I, 36 and 31, is supported by and between lead-ins 22 and 28 by means of the construction above described. When a suitable heating voltage is applied between the conductors 22 and 28, current passes through shield members 36 and and sleeve I6 and the sleeve I5 to the lower end of sleeve I5 and the lower metallic shield somewhat the conduction of heat from sleeve I5 to the end shields 20 and 2I, so that these shields are not at the very high temperature of sleeve I5. However, these annular shields are still at a rather high temperature which may be above the electron-emission temperature for the mate rial thereof. The imperforate shields or disks 36 and 31, according to this invention, serve to prevent emission of electrons from the interior of the sleeve I5, since the disks entirely cover the interior hollow space of said sleeve at both ends thereof,

In addition, the disks 36 and 31 serve to prevent emission of electrons toward the end caps from the annular shields 20 and 2|, which may be hot enough to emit electrons. Because of the fact that disks 36 and 31 are spaced from the corresponding shields 20 and 2|, 9. non-heat-conducting gap is provided therebetween, this gap being a vacuum gap or non-metallic gap. The metallic brackets 38 and 39 are of such small area that there is no appreciable conduction of heat therethrough from the annular members to the disk members. Due to the heat-insulating space between the annular members and the disk members, the disk members are maintained at all times at a temperature substantially less than that of the annular members, in fact one at which there is no appreciable electron emission from.

said disk members. Since the disk members have the same outer diameter as the annular members and are vertically aligned therewith, the disk members intercept and prevent electrons which might be emitted from the hotter annular members from reaching the end caps.

Another feature of this invention resides in the effective conduction of heat away from the shields, thus preventing such shields from reaching undesirably high temperatures. The shields 20 and 36 at the upper end of the cathode are connected directly to lead-in 22 by means of members 34 and 40. This allows heat to be efficiently conducted away from the shield members by the leadin 22, out of the envelope. The same holds true at the lower part of the cathode, since shields 2| and 31 thereat are connected directly to lead-in 26 by means of members 35 and 4 I.

A coupling loop 42 extends into the space between two of said plates 5, one end of said loop being connected to the inner end of a conducting pipe 43 hermetically sealed through the wall of the envelope I, substantially midway between the ends thereof, the other end of said loop being connected to a conductor 44 extending through said pipe 43 and sealed through a glass seal, not shown, at the outer end of said pipe 43. An additional conducting pipe, not shown, may be electrically connected to said pipe 43 to form with said conductor 44 a concentric line through which the high-frequency oscillations generated by the device, when it is energized and placed between magnetic poles I2 and I3, may be conducted to a suitable utilizing circuit.

Of course, it is to be understood that this invention is not limited to the particular details as described above, as many equivalents will suggest themselves to those skilled in the art.

What is claimed is:

1. An electron discharge device comprising: an envelope containing a cathode and an anode adjacent thereto; a perforate shield member attached to one end of said cathode and disposed intermediate said one end of said cathode and said envelope; an imperforate shield member spaced from said perforate member on the opposite side thereof from said cathode; and'means securing each of said shield members to a common lead-in support.

2. A cathode assembly, comprising a cathode in the form of a cylindrical sleeve, an annular shield member secured to one end of said sleeve, the outer diameter of said member being greater than the outer diameter of said sleeve, an imperforate shield member spaced from said perforate member on the opposite side thereof from said sleeve, and means securing each of said shield members to a common lead-in support.

3. An electron discharge device comprising: an envelope containing a cathode md an anode adjacent thereto; a pair of perforate shield members attached to opposite ends of said cathode, each being disposed intermediate its corresponding end of said cathode and said envelope; a pair of imperforate shield members, each being spaced from a corresponding one of said perforate members in the direction of said envelope; means securing the pair of shield members at one end of said cathode to a common lead-in support; and means securing the pair of shield members at the other end of said cathode to an opposite common lead-in support.

4. An electron discharge device comprising: an envelope containing a cathode and an anode adjacent thereto, said cathode including an electron-emissive portion in the form of a cylindrical sleeve; a pair of perforate metallic shield members secured and electrically connected to opposite ends of said sleeve, each being disposed intermediate its corresponding end of said sleeve and said envelope; a pair of imperforate metallic shield members, each being spaced from a corresponding one of said perforate members in the direction of said envelope; means securing and electrically connecting the pair of shield members at one end of said sleeve to a common leadin support; and means securing and electrically connecting the pair of shield members at the other end of said sleve to an opposite common lead-in support.

5. A cathode assembly, comprising a cathode in the form of a cylindrical sleeve, a pair of perforate shield members secured to opposite ends of said sleeve, the outer diameters of both said members being greater than the outer diameter of said sleeve, a pair of imperforate shield members each of which is spaced from a corresponding one of said perforate members in the direction away from said sleeve, means securing the pair of shield members at one end of said sleeve to a common lead-in support, and means securing the pair of shield members at the'other end of said sleeve to an opposite common lead-in support.

6. A cathode assembly, comprising a cathode in the form of a cylindrical sleeve, 9, perforate substantially planar shield member secured to one end of said sleeve, the plane of said member extending transversely to the longitudinal axis of said sleeve, an imperforate substantially planar shield member spaced from said perforate member on the opposite side thereof from said sleeve, the plane of said imperforate member being substantially parallel to the plane of said perforate member, and means securing each of said shield members to a common lead-in support.

7. A cathode assembly, comprising a cathode in the form of a cylindrical sleeve, a perforate substantially planar shield member secured to one end of said sleeve, the plane of said member extending'transversely to the longitudinal axis of said sleeve, an imperforate substantially planar shield member spaced from said perforate member on the opposite side thereof from said sleeve, the plane of said imperforate member'being substantially parallel to the plane of said perforate member, a lead-in support the longitudinal axis of which is transverse to the longitudinal axis of said sleeve, means rigidly securin said perforate member to said support, and means firmly securing one side of said imperiorate member to said support.

8. A cathode assembly, comprising a cathode in the form of a cylindrical sleeve, a perforate substantially planar shield member secured to one end of said sleeve, the plane of said member extending tranvcrsely to the longitudinal axis of said sleeve, an imperforate disk-like shield member spaced from said perforate member in the direction away from said sleeve, the plane of said disk-like shield member being substantiall parallel to the plane of said perforate member, a lead-in support the longitudinal axis of which is transverse to the longitudinal axis of said sleeve, means rigidly securing said perforate member to said support, means firmly securing one side of said disk-like shield member to said support, and a member positioned between the adjacent surfaces of said disk-like shield member and said perforate member, and secured thereto at the side diametrically opposite said one side of said disk-like shield member thereby spacing said disk member from said perforate member, said spacing member having a small area relative to the area of said disk member.

9. A cathode assembly, comprising a cathode in the form of a cylindrical sleeve, a pair of perforate substantially planar shield members secured to opposite ends of said sleeve, the planes of each of said members extending transversely to the longitudinal axis of said sleeve,- a pair of imperforate substantially planar shield members each of which is spaced from a corresponding one of said perforate members in the direction away from said sleeve, the planes of each of said imperforate members being substantially parallel to the planes of said perforate members. means securing the pair of shield members at one end of said sleeve to a common lead-in support, and means securing the pair of shield members at the other'end of said sleeve to an OPP site common lead-in support. 1

10. A cathode assembly, comprising a cathode in the form of an eiectron-emissive cylindrical sleeve, a pair of annular metallic shield members secured and electrically connected to opposite ends .pf said sleeve. the outer diameters of both said members being greater than the outer diameter of said sleeve, 8. pair of imperforate metallic shield members each of which is spaced from a corresponding one of'sald annular members in the direction away from said sleeve, means securing and electrically connecting the pair of shield members at one end of said sleeve to a common lead-in support, and means securing and electrically connecting the pair of shield members at the other end of said sleeve to an opposite common leall-in support.

11. A cathode assembly, comprising a cathode in the form of a cylindrical sleeve, an annular shield member secured to one end of said sleeve. the outer diameter of said member being greater than the outer diameter of said sleeve, an imperforate disk-like shield member spaced from said annular member on the opposite side thereof from said sleeve, the diameter of said disk member being substantiaiy equal to the outer diameter'of said annular member. and means securing each of said shield members to a common lead-in support.

12. A cathode assembly, comprising a cathode in the form of a cylindrical sleeve, a pair of perforate substantially planar shield members secured to opposite ends of said sleeve, the planes of each of said members extending transversely to the longitudinal axis of said sleeve, a pair of imperforate substantially planar shield members each of which is spaced from a correspondin one of said perforate members in the direction away from said sleeve, the planes of each of said imperforate members being substantially parallel to the planes of said perforate members, a pair of spaced parallel lead-in supports the longitudinal axes of which are transverse to the longitudinal axis of said sleeve, one of said supports being adjacent each end of said sleeve. means securing the pair of shield members at one end of said sleeve to one of said supports. and means securing the pair of shield members 'at the other end of said sleeve to the other of said supports.

HOMER G. ANDERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

